Combinations of zinc pyrithione and cuprous oxide are known to be excellent antifouling agents when formulated into paints and paint bases (i.e., the paint before pigment addition). Unfortunately, however, such paints have now been found to thicken or gel unacceptably within a few days at best, or a few hours, at worst, when formulated with typical commercial grades of zinc pyrithione in combination with cuprous oxide. Various solutions to the problem of gelation of paints containing zinc pyrithione in combination with cuprous oxide have been proposed. For example, U.S. Pat. No. 5,112,397 discloses a process for providing a gelation-inhibited paint which employs an organic amine and/or esterified wood rosin in order to impart the desired gelation-inhibition to the paint. Unfortunately, the organic amines are less desirable from an environmental standpoint than otherwise might be desired.
Accordingly, new, more environmentally friendly solutions to the above-discussed problem of unwanted gelation, with respect to paints containing zinc pyrithione in combination with cuprous oxide, would be highly desired by the paint manufacturing community, particularly since this combination of biocides provides excellent biocidal activity. The present invention provides one such solution.